Background Pressure-flow study combined with cystourethroscopy were used as the major method to define female bladder neck obstruction in China.However,the definition of urodynamics for female bladder outlet obstruction (BOO) is not clear so far.Video-urodynamic study (VUDS) would provide more information to define the female BOO,but it is not used commonly due to the limitation of video-urodynamic equipment in China.We attempted to find a better way for diagnosis of female BOO by performing VUDS.Methods VUDS and cystourethroscopy were performed in 38 women with signs and symptoms of difficult voiding from March 2008 to April 2010 in Beijing Chao-Yang Hospital.Bladder neck obstruction was defined by radiological evidence of narrowing bladder neck,voiding pressure greater than 20 cmH2O and maximum flow rate (Qmax) less than 12 ml/s.Transurethral incision of bladder neck was then performed on those patients.Follow-up examination (Qmax and residual urine) was recorded 3 months after operation.Results The mean time from its onset to diagnosis was (18.1±9.1) months in 38 patients.Average patient age was 36.1 years (range from 19 to 79 years).The mean Qmax was (10.6±4.7) ml/s and residual urine was (81.5±42.4) ml.Three out of 38 patients had obvious distal urethral stricture,eight of them suffered from definitely bladder neck contracture and the remaining 27 patients did not show obvious abnormalities measured by cystourethroscopy examination.For the 35 patients without urethral stricture,the most frequent findings of VUDS were high-voiding pressure plus low-flow rate and narrow bladder neck during voiding on simultaneous fluoroscopy examination.With video-urodynamics definition,32 patients were diagnosed as bladder neck obstruction with mean Qmax of (10.8±3.7) ml/s,residual urine of (76.9±32.7) ml and detrusor pressure at maximum flow (PdetQmax) of (50.7±19.1) cmH2O.Other three patients were suffered from detrusor hypocontractility.All 32 patients including eight with definitely bladder neck contracture and 24 with primary bladder neck obstruction received transurethral bladder neck incision.The symptom of difficult voiding was relieved.The postoperative follow-up showed that Qmax was (21.7±7.6) ml/s (P ＜0.01) and the residual urine was (23.2±17.6) ml (P ＜0.01 ).Conclusions The real cause of the obstruction for female patient with difficult voiding might be various.A full VUDS would give us valuable information for correct diagnosis in female patients with bladder neck obstruction.